However, the top-named concern is access to health care, with 23 percent calling it the nation's most- pressing health problem. Obesity ranks as the third most commonly named problem; the cost of health care ranks second, with 19 percent.

Health care access and cost have been the top two concerns since 2003, according to Gallup. Polls conducted in 2001 named bioterrorism as the top concern, and AIDS topped the list several times during the late 1980s and 1990s.

Ranking fourth in this year's poll, with 13 percent, is cancer.

According to the Centers for Disease Control and Prevention, 35.7 percent of U.S. adults, and 17 percent of children are obese.

Unless the nation's growing obesity rate is curbed, "it is likely this issue will continue to make its way to the top of Americans' list of the most urgent health problems in the country," Gallup said.

Pass it on: An increasing number of people say that obesity is the biggest health problem in the U.S.